Double life shaft seal

ABSTRACT

A double life shaft seal includes a seal case and an elastomeric sealing annulus having first and second seal lips adapted to be sequentially contacted by a rotating shaft. A tensioned garter spring is initially located on the sealing annulus so as to bias the first seal lip into operative sealing engagement with the shaft to provide a first service life, the spring being positioned thereat by spring biased expanded constriction ring restrained against axial movement by engagement with blocking lugs on the seal case. After predetermined wear of the first seal lip, the constriction ring contracts in diameter and loses contact with the blocking lugs at which time the ring and the garter spring are axially shifted to a second position wherein the garter spring is located so as to bias the second seal lip into operative sealing engagement with the shaft to provide a second service life.

lJnite States et [19] McEwen 2,3 I 6,7 I 3 3,099,454 3,207,52l

DOUBLE LIFE s I Inventor:

SEAL John C. MclEwen, Indianapolis, Ind.

General Motors Detroit, Mich.

Filed: Nov. 5, 1971 Appl. No.: 195,971

Assignee: Corporation,

References Cited UNITED STATES PATENTS Procter ..277/l53 Walinski-v277/1512 X Dega ..277/58 X [451 Apr. 17, 1973 Primary Examiner-SamueIB. Rothberg Att0rney l. L. Carpenter et al.

ABSTRACT A double life shaft seal includes a seal case and anelastomeric sealing annulus having first and second seal lips adapted tobe sequentially contacted by a rotating shaft. A tensioned garter springis initially located on the sealing annulus so as to bias the first seallip into operative sealing engagement with the shaft to provide a firstservice life, the spring being positioned thereat by spring biasedexpanded constriction ring restrained against axial movement byengagement with blocking lugs on the seal case. After predetermined wearof the first seal lip, the constriction ring contracts in diameter andloses contact with the blocking lugs at which time the ring and thegarter spring are axially shifted to a second position wherein thegarter spring is located so as to bias the second seal lip intooperative sealing engagement with the shaft to provide a second servicelife.

3 Claims, 5 Drawing Figures and, accordingly, fails.

DOUBLE LIFE SHAFT SEAL The present invention relates to fluid seals and,in particular, to shaft seals having plural independent sealing surfacesfor preventing the flow of fluid.

Fluid seals, of the type conventionally used for sealing between arotating shaft arida stationary housing, generally comprise a casemounted on the housing, an elastomeric sealing annulus attached to thecase having a sealing lip adapted to engage the shaft, and a helicallycoiled garterspring retained on the outer surface of the sealing annulusfor biasing the seal lip with engagement to the shaft. The garter springprovides sufflcient inward biasing to maintain a lip pressure thatprevents fluid leakage between the shaft and the lip. As the seal lipwears in usage, the lip pressure decreases and together with associatedproblems such as sea] lip hardeningand cracking such that the lip is nolonger able to freelyconform with the mating surface of the shaft. Atthis point, the seal can no longer contain fluid The present inventionprovides a second service life for the fluid seal by incorporating anindependent secondary sealing surface which becomes operative afterpredetermined wear of the original sealing surface. More particularly,the sealing annulus has a pair of axially spaced seal lips, each ofwhichis adapted to engage the shaft. During the initial operating period, oneof the lips engages the shaft while the other lip is slightly spacedtherefrom. A shiftagle garter spring provides the requisite biasingforce on the first lip to maintainvthe sealing contact. A spring biasedradially expanded split constriction ring locates the spring at thisposition. The ring is held at this first position by engagementwithblocking lugs on the seal case. As the first seal lip progressivelywears, the diameter of the constriction ring contracts. Afterpredetermined wear of the first seal lip,.the constriction ring'losescontact with the blocking lugs and is biased to a second positionwherein the garter spring is radially inwardly biasing the second lipinto operative contact with the shaft. Thus, it will be appreciatedthati t his second and independent sealing lip provides a second servicelife for the fluid seal.

The above and other features of the present invention will be apparentto one skilled in the art upon reading the following detaileddescription, reference being made to the accompanying drawingsillustrating a preferred embodiment of the present invention in which: v

FIG. 1 is a partially sectioned view of the double life shaft seal madein accordance with the present invention shown mounted between a housingand a shaft;

FIG. 2 is a fragmentary view taken along line 22 of FIG. 1 showing theengagementbetween the blocking lugs and the constriction ring during thefirst service life of the seal;

FIG. 3 is an enlarged sectional view showing the seal in the firstservice life position;

FIG. 4 is a view similar to FIG. 3 showing the seal in the secondservice life position; and

'FIG. 5 is a partial perspective view of the subject seal showingdetails of construction.

Referring to FIG. 1, the double life shaft seal made in accordance withthe present invention is mounted in the annular space between an innercylindrical surface 12 of an axial bore in a stationary housing 14 andthe outer cylindrical surface 16 of a rotating shaft 18. The seal 10serves to prevent the flow of fluid from a fluid chamber 20 to an airchamber 22. Although the present invention is shown and described withreference to a shaft installation, it will be appreciated that theinvention is equally adaptable in other sealing installations such asface seals and reciprocating seals.

The double life shaft seal 10 generally comprises a case 24, a sealingannulus 26, a constriction ring 28, a ring biasing spring 30, and agarter spring 32.

The sealing annulus 26 is formed of a suitable elastomeric material andgenerally comprises a cylindrical outer sleeve 34 and a cylindricalinner sealing sleeve 36, which are interconnected by an annular web 37.As shown in FIG. 3, the inner'surface of the sealing sleeve 36 isprovided with a pair of sharp radial seal lips 38 and 40 individuallydefined by pairs of radially inwardly converging frustoconical surfaces.The vertex of the rear or first seal lip 38 and the vertex of the frontor second seal lip 40 define first and second sealing surfaces 41 42respectively, which have an interference fit with the surface 16 of theshaft 18. In initial installation, however, the first seal lip 38compressively engages the surface 16 and the resulting expansion of thesleeve 36 in combination with therearward radial biasing action of theconstriction ring 28 slightly radially spaces the sealing surface 42 ofthe seal lip 40 from the surface 16. In achievingthis initial operatingrelationship, the lips 38 and 40 may be of the same diameter or, ifdesired, the lip 40 can have a slightly larger diameter than the lip 38.However, both lips must be able to independently operatively contact theshaft 18.

The garter spring 32 is conventional in construction and comprises acircumferentially continuous helical wire. The spring 32 is radiallyoutwardly tensioned expanded to provide a radially inwardly biasingforce to the sealing sleeve 36. The spring 32 is shiftably retained onthe outer surface of the sealing annulus 26. In the first service lifeposition shown in FIG. 3, the spring 32 is axially located in operativebiasing relationship over I the first seal lip 38 by the constrictionring 28. In the second service life position shown in FIG. 4, the spring32 is located in operative biasing relationship over the 7 second seallip 40 by a radially outwardly projecting annular shoulder 43 at thefront of the sealing sleeve 36. As hereinafter explained, the garterspring 32 is automatically shifted after predetermined wear of thesealing surface 41 of the first seal lip 38 from the FIG. 3 position tothe FIG. 4 thereby providing selective biasing of the seal lips 38 and40.

The seal case 24 comprises a metallic stamping and includes acylindrical outer section 44 which fric- .tionally engages the surface12 of the housing .14. The

tion 56 which slidably engages the outer surface of the sealing sleeve36 and a radially outwardly spaced front section 58. The sections 56 and58 are interconnected by an annular shoulder 59. In operativerelationship over the sealing sleeve 36, the constriction ring 28 isradially outwardly expanded to an enlarged diameter. In the firstservice life position shown in FIG. 3, the front section 58 is adiametral interference with the blocking lugs 50. Accordingly, theconstriction ring 28 is axially locked with this position against thebiasing of the helically coiled ring biasing spring 30. However, asfrictional wear takes place at the first seal lip 38, the diameter ofthe sealing annulus at this position gradually decreases. During thistime, the constriction ring 28 will contract in diameter to take up thewear at the seal lip 38 After predetermined wear of the sealing surface41, the front section 58 contracts sufficiently in diameter to clear orslip under the blocking lugs 50. Thereupon, the spring 30 will bias theconstriction ring 28 and the garter spring 32 forwardly along the outersurface of the sealing sleeve 36 to the FIG. 4 or second surface lifeposition whereat movement is restrained by engagement with the shoulder43.

At the first service life position, the radial biasing is providedprimarily by the garter spring 32. However, the constriction ring 28will provide a small amount of biasing. Additionally, the biasing by thering 28 will provide an inward biasing on the rear portion of thesealing sleeve 36, which will tend to pivot the latter about the lip 38to provide forces tending to lift the seal lip 40 from the surface 16.In the second service life position, the garter spring 32 providesoperative biasing of the second seal lip 40 against surface 16 of theshaft 18 and the resiliency of the web 37 and the outer sleeve 34 willtend to slightly space the lip 38 from the surface 16. Accordingly, asecond and independent seal lip is provided for the seal which willfunction substantially in the same manner as the original lip.

While the present invention has been described with reference toautomatically operative means for selectively biasing the lip, it willbe appreciated that manual means can be provided for shifting the spring32 between an initial operative position at the first lip 38 to a secondoperative position at the second lip 40 after predetermined wear of thefirst sealing surface 41.

Although only one form of this invention has been shown and described,other forms will be readily apparent to those skilled in the art.Therefore, it is not intended to limit the scope of this invention bythe embodiment selected for the purpose of this disclosure but only bythe claims which follow.

What is claimed is:

l. A fluid seal comprising:

a casing member;

a flexible sealing element connected to said casing member, said sealingelement having a pair of annular sealing surfaces facing a surface to besealed, one of the sealing surfaces adapted to normally operativelyengage said surface to be sealed;

shiftable means operable at a first position for biasing said one ofsaid sealing surfaces into engagement with said surface to be sealed andoperable at a second position for biasing the other of said sealingsurfaces into engagement with said surface to be sealed; I meansassociated with said shiftable means for holding the latter at saidfirst position until predetermined wearing of said one of said sealingsurfaces and thereafter releasing said shiftable means;

and means for moving said shiftable means to said second position aftersaid releasing whereby said other of said sealing surfaces isoperatively biased into engagement with said surface to be sealed.

2. A fluid seal for sealing the space between relatively rotatingmembers comprising: a casing member mounted on one of the members; aflexible sealing element connected to said casing member; a pair ofannular sealing lips projecting toward the other of said members, one ofthe lips adapted to normally engage said other of said members with theother of said lips being initially spaced therefrom; first spring meansslidably retained on said sealing element for selectively biasing saidlips; a shiftable element on said sealing element engaging said firstspring means, said shiftable element being movable from a normal firstposition wherein said first spring means operatively biases one of saidlips to a second position wherein said first spring means operativelybiases said other of said lips; stop means associated with the shiftableelement for holding the latter at said first position untilpredetermined wearing of said one of said lips; and second spring meansbetween said casing member and said shiftable member for shifting thelatter to said second position after said predetermined wearing wherebysaid other of said lips engages said other of said members to provide asecond seal life.

3. A dual life shaft seal for sealing the space between a relativelyrotating shaft and housing comprising: an annular case mounted on saidhousing; a sealing annulus formed ofa flexible material connected tosaid case, said sealing annulus including a cylindrical sleeve spacedfrom the shaft; first and second seal lips formed on the inner surfaceof and axially spaced along said sleeve, said first andsecond seal lipshaving first and second sealing surfaces individually defined byradially inwardly converging frustoconical surfaces, both of saidsealing surfaces adapted to engage the shaft with said first sealingsurface normally engaging the shaft and said second sealing surfacebeing initially radially spaced therefrom; a tensioned helical springslidably retained on the outer surface of said sleeve for radiallyinwardly biasing either of said lips; a split annular contractable ringslidably received over said outer surface of said sleeve and engagingsaid helical spring; an inwardly projecting tab on said case normallylocating said ring and said helical spring at a first position whereinsaid spring radially inwardly biases said first seal lip therebyproviding a first service life for said seal, said ring contracting indiameter upon wearing of said first seal lip and disengaging from saidtab after predetermined lip wear; spring biasing means acting on saidring and shifting said ring and said spring after said predetermined lipwear to a second position wherein said helical spring radially inwardlybiases said second lip against the shaft to provide a second servicelife for said seal.

1. A fluid seal comprising: a casing member; a flexible sealing element connected to said casing member, said sealing element having a pair of annular sealing surfaces facing a surface to be sealed, one of the sealing surfaces adapted to normally operatively engage said surface to be sealed; shiftable means operable at a first position for biasing said one of said sealing surfaces into engagement with said surface to be sealed and operable at a second position for biasing the other of said sealing surfaces into engagement with said surface to be sealed; means associated with said shiftable means for holding the latter at said first position until predetermined wearing of said one of said sealing surfaces and thereafter releasing said shiftable means; and means for moving said shiftable means to said second position after said releasing whereby said other of said sealing surfaces is operativelY biased into engagement with said surface to be sealed.
 2. A fluid seal for sealing the space between relatively rotating members comprising: a casing member mounted on one of the members; a flexible sealing element connected to said casing member; a pair of annular sealing lips projecting toward the other of said members, one of the lips adapted to normally engage said other of said members with the other of said lips being initially spaced therefrom; first spring means slidably retained on said sealing element for selectively biasing said lips; a shiftable element on said sealing element engaging said first spring means, said shiftable element being movable from a normal first position wherein said first spring means operatively biases one of said lips to a second position wherein said first spring means operatively biases said other of said lips; stop means associated with the shiftable element for holding the latter at said first position until predetermined wearing of said one of said lips; and second spring means between said casing member and said shiftable member for shifting the latter to said second position after said predetermined wearing whereby said other of said lips engages said other of said members to provide a second seal life.
 3. A dual life shaft seal for sealing the space between a relatively rotating shaft and housing comprising: an annular case mounted on said housing; a sealing annulus formed of a flexible material connected to said case, said sealing annulus including a cylindrical sleeve spaced from the shaft; first and second seal lips formed on the inner surface of and axially spaced along said sleeve, said first and second seal lips having first and second sealing surfaces individually defined by radially inwardly converging frustoconical surfaces, both of said sealing surfaces adapted to engage the shaft with said first sealing surface normally engaging the shaft and said second sealing surface being initially radially spaced therefrom; a tensioned helical spring slidably retained on the outer surface of said sleeve for radially inwardly biasing either of said lips; a split annular contractable ring slidably received over said outer surface of said sleeve and engaging said helical spring; an inwardly projecting tab on said case normally locating said ring and said helical spring at a first position wherein said spring radially inwardly biases said first seal lip thereby providing a first service life for said seal, said ring contracting in diameter upon wearing of said first seal lip and disengaging from said tab after predetermined lip wear; spring biasing means acting on said ring and shifting said ring and said spring after said predetermined lip wear to a second position wherein said helical spring radially inwardly biases said second lip against the shaft to provide a second service life for said seal. 